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United States Patent | 5,241,603 |
Akagiri ,   et al. | August 31, 1993 |
The present invention relates to a digital signal encoding apparatus in which an input digital signal has its frequency range divided into a number of frequency bands so that the bandwidths are broader at higher frequencies. A first allowable noise level based on the energy levels in the respective bands, and a second allowable noise level based on the energies of the signals temporally adjacent to the signals of a frequency band under consideration, are set. Signal components of each frequency band are quantized with a number of bits corresponding to a difference between an output synthesized from the first and second noise levels and the energy level of each frequency band. In this manner, the bit rate may be lowered while deterioration in the sound quality is minimized.
Inventors: | Akagiri; Kenzo (Kanagawa, JP); Tsutsui; Kyoya (Kanagawa, JP); Fujiwara; Yoshihito (Kanagawa, JP) |
Assignee: | Sony Corporation (Tokyo, JP) |
Appl. No.: | 703830 |
Filed: | May 21, 1991 |
May 25, 1990[JP] | 2-133980 |
Current U.S. Class: | 704/205; 704/501 |
Intern'l Class: | G10L 005/00 |
Field of Search: | 381/29-37 395/2 |
4896362 | Jan., 1990 | Veldhuis | 381/37. |
4972484 | Nov., 1990 | Theile et al. | |
5105463 | Apr., 1992 | Veldhuis | 381/30. |
Rundfunktechnische Mitteilungen vol. 33, No. 4, Aug. 1989, Norderstedt DE pp. 149-154. WO-A-8-804 117 (Bayerische Rundfunkwerbung p. 4, line 29-p. 5, line 1, p. 10, line 25-p. 11, line 11, p. 15, line 1-line 15, p. 34, line 23-p. 35, line 17. Bell System Technical Journal vol. 56, No 5, May 1977, New York US pp. 747-769. |